The present invention is directed to a grid tee for a suspended ceiling or the like, which has a central web, a continuous bead on one edge of the web and a pair of flanges extending outwardly from the other edge. The bead has a circular cross section with a substantially continuous outer layer to provide a continuous surface on a surface facing away from the flanges and, in order to concentrate more metal in the bead, portions of the surface of the bead are two layers thick connected by a reversed bend.
Grid tees for suspended ceiling systems have been used for many years. Usually, the grid tee is formed by a sheet of material which has been bent to form a bead along one edge of a central web and opposed or outwardly extending flanges adjacent the other edge so that the cross section of the tee has an inverted T configuration. It is known to bend the sheet so that the web has two thicknesses and the flanges are each a single layer extending outward, which flanges may be covered by a cap strip so that the portion exposed to the occupants of the room can have any desired finish or color.
Recently, it has been suggested to form the grid tee out of a metal strip with a thinner gauge than previously. However, to maintain the rigidity of the component and to prevent rotation or buckling due to loading, arrangements have been made or suggested for reinforcing the bead or bulb of the tee. Examples of two approaches of forming a grid tee out of thin gauge metal with a reinforced bulb are disclosed in a patent to David F. Mieyal, U.S. Pat. No. Re. 31,528; and the U.S. Patent to Worley et al, U.S. Pat. No. 4,520,609. In the Reissue Patent, the reinforcing is by putting a second or an additional strip of metal in the area of the strip of metal which will be bent into the bulb. While this procedure allows utilizing a heavier sheet of metal for the insert than the rest of the strip used for the tee, there are problems with maintaining the additional sheet in the desired position while bending and forming the main strip into the grid tee.
In the solution suggested by the Worley et al patent, the top of the hollow bead or bulb has a plurality of folds so that a larger amount of material is concentrated at the extremity of the bulb relative to the web to increase the strength of the bulb and to shift the shear center into the web of the tee. However, the solution in Worley results in abutting edges of folds on the outer or top surface of the bead, and these abutting edges of the folds or seams may tend to buckle, due to bending of the tee.
Another type of reinforced bead is disclosed in the copending allowed U.S. patent application Ser. No. 296,853, filed Jan. 13, 1989, which issued as U.S. Pat. No. 4,852,325 and was a continuation of U.S. Ser. No. 112,549, abandoned filed Oct. 26, 1987, and whose disclosure is incorporated by reference. In this copending application, various species were mentioned in which either the bead had a hollow configuration which was either rectangular or triangular or the bead had a solid configuration of a plurality of layers.